Easwaran, Regularity and Hyperreal Credences (a really excellent piece that'll give you a sense of the pros and cons of using infinitesimals to do various things)
On Jeffrey Conditionalization (it is worth noting there are also a number of papers discussing the possibility of a dutch book defense of Jeffrey conditionalization):
Jeffrey, Probable Knowledge - this can be found in the volume Probability and the Art of Judgment which has a number of papers by Jeffrey about the "Radical Probabilism" view